<ul style="font-weight: bold; padding: 0;margin: 10px;">
  <?php foreach($form->getWidgetSchema()->getPositions() as $widgetName): ?>
    <?php if($form[$widgetName]->hasError()): ?>
    <li style="color:#cc6666;"><?php echo $form[$widgetName]->getError(); ?></li>
    <?php endif; ?>
  <?php endforeach;?>
</ul>